Enzymes

R.C. Gupta
Professor and Head
Dept. of Biochemistry
National Institute of Medical Sciences
Jaipur, India
Enzymes

A vast multitude of chemical reactions
occur in living organisms
It is these reactions that keep the
organism going
These reactions would occur at extremely
low velocities in the absence of catalysts
EMB-RCG

EMB-RCG
Common catalysts used in non-living
systems are:
Acids Alkalis Metals
These are not suitable for living
organisms because of their:
Toxicity Lack of specificity

Biological catalysts should be:
Safe (non-toxic)
Specific (generally catalyzing
one reaction only)
Capable of adjusting their
catalytic activity
All these properties are present in
enzymes
EMB-RCG

Enzymes were first discovered in
yeast (enzyme means ‘in yeast’)
EMB-RCG
Chemically, all enzymes were found to be
proteins
They could catalyze reactions outside
the living organisms also
They were later found in other living
organisms as well

Definition
EMB-RCG
But this definition is not entirely correct
Enzymes are protein catalysts that catalyse
chemical reactions in biological systems
Some RNA molecules (ribozymes) have
been found to catalyze some reactions

The reactant on which the enzyme acts is
known as the substrate of the enzyme
EMB-RCG
Substrate Product
Enzyme
The enzyme converts the substrate into a
product or products

EMB-RCG
If an enzyme catalyses a number of
reactions, it will be impossible to
regulate individual reactions
Enzyme specificity
However, the enzymes are highly
specific

EMB-RCG
Generally, one enzymes catalyses only
one reaction
This is of crucial importance for
regulation of metabolic pathways

EMB-RCG
Enzyme specificity may have
the following orders:
Group specificity
Substrate specificity
Stereo-specificity

EMB-RCG
Group specificity
Enzyme is specific for a bond but not
for the actual substrate
Group-specific or bond-specific
enzymes are commonly present in
digestive secretions

EMB-RCG
For example, pepsin is specific for
peptide bond but not for any protein
Thus, a large variety of dietary proteins
can be digested by the same enzyme
Trypsin, chymotrypsin, nucleases, lipases
and glycosidases are other examples

EMB-RCG
Some group-specific enzymes have a
slightly higher degree of specificity
For example, aminopeptidase
hydrolyses only N-terminal peptide bond
Carboxypeptidase hydrolyses only the
C-terminal peptide bond
Endopeptidases hydrolyse the internal
peptide bonds only

H2N–Phe–Ala–Ser–Cys–Gly–Asp–Arg–Val–Leu–Glu–COOH
Amino-
peptidase
Endo-
peptidase
Carboxy-
peptidase

EMB-RCG
Most enzymes are specific for a chemical
bond/group as well as the substrate
For example, glucokinase and fructokinase
are substrate-specific enzymes
They transfer a phosphate group from ATP
to one specific substrate
Substrate specificity

Glucose Glucose-6-Phosphate
Glucokinase
ATP ADP
Fructose Fructose-1-Phosphate
Fructokinase
ATP ADP
EMB-RCG

EMB-RCG
Stereo-specificity
Many biomolecules exhibit stereo-
isomerism
Examples are carbohydrates and
amino acids
Enzymes acting on these are specific
for one stereo-isomer

EMB-RCG
Mammalian enzymes acting on carbo-
hydrates are generally specific for
D-isomers
Those acting on amino acids are
generally specific for L-isomers
Exceptions are racemases which
inter-convert the D- and L-isomers

EMB-RCG
COOH
I
H2N – C – H
I
CH3
COOH
I
H – C – NH2
I
CH3
Alanine
racemase
L-Alanine D-Alanine
Stereospecificity – An exception

Some enzymes require a non-protein
substance for their catalytic activity
If the non-protein substance is
organic, it is known as a coenzyme
If the non-protein substance is
inorganic, it is known as a cofactor
EMB-RCG
Coenzymes and cofactors

EMB-RCG
The coenzyme or the
cofactor may be:
An integral part of the enzyme
or
Its presence may be required
during the reaction

The protein portion of an enzyme that
requires a coenzyme is called apoenzyme
Apoenzyme + Coenzyme → Holoenzyme
EMB-RCG
Apoenzyme combines with coenzyme to form
the active holoenzyme

EMB-RCG
The coenzymes generally contain vitamins
of B-complex family
Some are converted into coenzymes e.g.
thiamin, riboflavin, niacin, pantothenic acid,
pyridoxine, folic acid and vitamin B12
Some act as coenzymes by themselves
e.g. biotin

EMB-RCG
Oxidation-reduction
Transamination
Phosphorylation
Coenzymes are generally required
in group transfer reactions e.g.

EMB-RCG
Coenzymes can be divided into
two groups:
Coenzymes
involved
in transfer of
hydrogen
Coenzymes
involved in transfer
of groups other
than hydrogen

Coenzymes
involved in
transfer of
hydrogen:
Flavin mononucleotide (FMN)
Flavin adenine dinucleotide (FAD)
Nicotinamide adenine dinucleotide
(NAD+)
Nicotinamide adenine dinucleotide
phosphate (NADP+)
Lipoic acid
Coenzyme Q

Coenzymes
involved in
transfer of
groups
other than
hydrogen:
Thiamin pyrophosphate (TPP)
Coenzyme A (Co A)
Pyridoxal phosphate (PLP)
Tetrahydrofolate (H4- Folate)
Cobamides (B12- Coenzymes)
Lipoic acid
Biotin
ATP & similar nucleotides

EMB-RCG
Role of coenzymes
The enzyme acts upon its substrate, and
converts it into a product
Coenzyme acts as a co-substrate or a second
substrate in the group transfer reactions
The coenzyme either donates or accepts
the group that is being transferred

EMB-RCG
In the second reaction, the coenzyme NAD+ acts
a second substrate and accepts the hydrogen
atoms
In the first reaction, the coenzyme ATP acts as
a second substrate and donates a phosphate
group
CH2‒OH
CH2‒OH
CH‒OH
Glycerol
CH2‒OH
CH2‒O‒
CH‒OH
CH2‒OH
CH2‒O‒
C = O
ATP
Glycerol
kinase
ADP
Glycerol-3-
phosphate
Dihydroxy-
acetone
phosphate
Glycerol-3-
phosphate
dehydrogenase
NAD+ NADH
+ H+

The chemical change in the coenzyme is
opposite to that in the substrate
EMB-RCG
Thus, they act only as carriers, and regain their
original form at the end of the reaction
Pyridoxal phosphate, for example, acts as a
carrier of amino group in transamination
Some coenzymes accept a chemical group from
one substrate and donate it to another

EMB-RCG
Aspartate Glutamate
Oxaloacetate a-Ketoglutarate
Pyridoxal phosphate
Pyridoxamine phosphate
Glutamate oxaloacetate
transaminase (GOT)

Pyridoxal phosphate first accepts the amino
group from aspartate, and is converted into
pyridoxamine phosphate
Pyridoxamine phosphate then transfers the
amino group to a-ketoglutarate, and is
converted into pyridoxal phosphate
In the coupled reaction, aspartate is converted
into oxaloacetate, and a-ketoglutarate is
converted into glutamate
EMB-RCG

EMB-RCG
Aspartate + a-Ketoglutarate Oxaloacetate + Glutamate
GOT
PLP
Though pyridoxal phosphate is a reactant,
the reaction is usually shown as:
The coenzyme goes back to its original
form at the end of the reaction

EMB-RCG
Sometimes, the change in the coenzyme is
more important than that in the substrate
In glycolysis, glucose is converted into
pyruvate, and NAD+ is reduced in one
reaction
Reduced NAD+ transfers its hydrogen atoms
to oxygen, and NAD+ is regenerated

EMB-RCG
Here, regeneration of NAD+ is more important for
continuation of glycolysis
One more reaction occurs in which pyruvate is
reduced to lactate, and NADH is oxidised to NAD+
If the conditions are anaerobic, NAD+ cannot be
regenerated due to lack of oxygen

NAD+
NADH+H+
Glucose
↓
↓
Glyceraldehyde-3-P 1,3-Biphosphoglycerate
↓
↓
↓
↓
Lactate (Anaerobic) Pyruvate (Aerobic)

Enzyme nomenclature and classification
EMB-RCG
The nomenclature of enzymes has undergone
many changes over the years
The names assigned to enzymes in the
beginning were very vague and uninformative
Some of the early names are pepsin,
ptylin, zymase etc
These indicate neither the substrates nor the
type of reaction catalyzed by the enzyme

EMB-RCG
Later on, a slightly more informative nomen-
clature was adopted
Suffix -ase was added to the name of
the substrate e.g. lipase, protease etc
Still the type of reaction catalyzed by the
enzyme remained unclear

EMB-RCG
Nomenclature was modified further, to include
the name of the substrate followed by the
type of reaction ending with -ase
This resulted in names like lactate dehydro-
genase, pyruvate carboxylase, glutamate
decarboxylase etc
Even these names do not give complete
information, for example whether a coenzyme
is required or a byproduct is formed

EMB-RCG
To make the names of enzymes informative and
unambiguous, International Union of Biochemistry
(IUB) formed an Enzyme Commission
The enzyme commission proposed a method of
nomenclature and classification of enzymes
which is applicable to all living organisms

According to IUB system:
• The enzymes have been divided into six
classes (numbered 1 - 6)
• Each class is divided into subclasses
• Subclasses are divided into
subsubclasses
• Subsubclasses are divided into
individual enzymes

EMB-RCG
Nomenclature
The name of the enzyme has two parts
The first part includes the name(s) of the
substrate(s) including substrate (coenzyme)
The second part includes the type of
reaction ending with -ase
If any additional information is to be given,
it is put in parenthesis at the end

For example, the enzyme having the trivial
name glutamate dehydrogenase catalyzes
the following reaction:
L-Glutamate + NAD(P)+ + H2 O →
a-Ketoglutarate + NAD(P)H + H+ + NH3
According to IUB system, this enzyme is
known as L-Glutamate: NAD(P) oxido-
reductase (deaminating)
EMB-RCG

EMB-RCG
The amino group of L-glutamate is released as
ammonia
NAD+ or NADP+ is required as a co-substrate
This enzyme acts on L-glutamate
The IUB name shows that:
Type of reaction is oxidoreduction i.e. L-glutamate is
oxidised and the co-substrate is reduced

EMB-RCG
Moreover, each enzyme has been given
a code number consisting of four digits:
First digit shows the number of the
class
Second digit shows the number of the
subclass
Third digit shows the number of the
subsubclass
Fourth digit shows the number of the
enzyme

EMB-RCG
The code number of L-glutamate: NAD(P)
oxidoreductase (deaminating) is EC 1.4.1.3
This shows that is it the third enzyme of
subsubclass 1 of subclass 4 of class 1
EC is the acronym for Enzyme Commission

EMB-RCG
The enzymes are
divided into six
classes in IUB
classification:
Oxidoreductases
Transferases
Hydrolases
Lyases
Isomerases
Ligases

EMB-RCG
Oxidoreductases
These are the enzymes that catalyze
oxidation-reduction reactions
One of the substrates is oxidised
and the other is reduced
Different subclasses act on
different chemical groups
Groups undergoing the reaction include
–CH=CH–, >CH–OH, >C=O, >CH–NH2 etc

EMB-RCG
Examples of oxidoreductases are:
Glutamate dehydrogenase
Lactate dehydrogenase
Malate dehydrogenase
Glycerol-3-phosphate dehydrogenase

EMB-RCG
Transferases
These enzymes transfer a group other than
hydrogen from one substrate to another
Such groups include methyl group, amino
group, phosphate group, acyl group,
glycosyl group etc

EMB-RCG
Examples of transferases are:
Hexokinase
Glucokinase
Glutamate oxaloacetate transaminase
Ornithine carbamoyl transferase

EMB-RCG
Hydrolases
These enzymes hydrolyse various bonds
such as peptide, ester, glycosidic bonds etc
They are commonly found in the digestive
secretions and lysosomes
They hydrolyse carbohydrates, lipids,
proteins etc

EMB-RCG
Examples of
hydrolases are:
Amylase
Lipase
Pepsin
Ribonuclease

EMB-RCG
Lyases
These enzymes remove chemical
groups from substrates by
mechanisms other than hydrolysis
The groups removed may be water,
amino group, carboxyl group etc

EMB-RCG
Examples of
lyases are:
Aldolase
Enolase
Fumarase

Isomerases
These enzymes catalyse inter-
conversion of isomers of compound
Substrates include aldose-ketose
isomers, stereo-isomers etc
EMB-RCG

Examples of isomerases are:
Alanine racemase
Triose phosphate isomerase
Phosphohexose isomerase
Ribose-5-phosphate
ketoisomerase
EMB-RCG

Ligases
These enzymes ligate or bind two
substrates together
Binding occurs by a covalent bond
A source of energy is required e.g. a
high-energy phosphate
EMB-RCG

Examples of ligases are:
Glutamine synthetase
Squalene synthetase
Acetyl CoA carboxylase
EMB-RCG

At temperatures above absolute zero (– 273°C),
molecules are in constant motion because of
their kinetic energy
EMB-RCG
A chemical reaction occurs when molecules of
reactants collide with each other in the correct
orientation (kinetic theory of reaction)
Mechanism of action of enzymes

The greater the frequency of collisions
between the reactant molecules, the greater
will be the rate of reaction
EMB-RCG
The frequency of collisions can be increased
by raising the temperature

EMB-RCG
Rise in temperature
would increase:
Molecular motion
Frequency of collisions
Rate of reaction

Energy input required to reach the critical
level is known as the energy of activation
Energy level of reactants has to be raised
to a critical level for the reaction to occur

In living organisms, the enzymes provide
an alternate pathway for the reaction
Enzymes lower the energy of activation
The option of raising temperature is
not available in living organisms

The enzyme molecules are much larger than
their substrates
EMB-RCG
Enzyme-substrate interaction
The substrate binds to this site forming an
enzyme-substrate (ES) complex
An enzyme possesses a specific binding site
for its substrate(s) known as the substrate site

Substrates
bind to enzyme
Bond is
formed
Product is
released
The binding may bring two substrates in
close proximity (bond-forming distance) in
the correct orientation so that a bond is
formed between the two

The binding of a substrate to the enzyme
many induce a strain in the substrate
As a result, a bond is broken in the
substrate
The substrate is split into two or more
products which are released

Enzyme ‒
Substrate ‒
Products ‒
Substrate binds
to enzyme
A strain occurs in the
substrate; a bond is
broken
Substrate splits into
products which are
released

On binding of two substrates to the enzyme,
a chemical group may be transferred from
one substrate to another

The catalytic action of the enzyme may
be exerted by:
Cofactors
Coenzymes
Some amino acid residues in the
substrate site
EMB-RCG

In the reaction catalysed by carbonic anhydrase,
the cofactor (zinc) catalyses
the reaction
‒ Zn++
H+ + HCO3
‒
H2O
‒ Zn++
...‒O + H+
H
I
CO2
‒ Zn++
+ O‒C‒O‒ + H+
H
I
II
O
‒ Zn++
...O‒C‒O
H
I
II
O
H
I
‒ Zn++
...O + C = O...H+
H
I
II
O
‒

In transamination reactions, the coenzyme
(pyridoxal phosphate) is involved in catalysis
Pyridoxal phosphate is present at the
substrate site
It accepts an amino group from an amino
acid, and then donates it to a keto acid
EMB-RCG

Common amino acid residues in the substrate
site are serine, histidine, cysteine, aspartate etc
Serine proteases are proteolytic enzymes in
which serine residues catalyse hydrolysis
Examples of serine proteases are trypsin,
chymotrypsin, thrombin etc
EMB-RCG

The first model was
proposed by Emil
Fischer
Also known as
rigid template
model
A different model
was later proposed
by Koshland
Also known as
induced fit
model
Models of enzyme conformation
EMB-RCG

EMB-RCG
Fischer’s
model
Conformation of enzymes
very rigid
Lock and key type of
complementarity between
substrate and enzyme
Complementarity responsible
for specificity of enzymes
Lock
Key

Fischer’s model did not agree with
certain experimental findings
obtained later
Conformation of enzyme was found to
change when it combined with its substrate
EMB-RCG

Before substrate binding After substrate binding
Substrate Enzyme

Koshland’s model conforms to known findings
In the absence of substrate, complementarity
between enzyme and substrate is not
apparent
Approach of substrate induces change in
conformation of the enzyme
The substrate site becomes
complementary to the substrate

The substrate binds to the enzyme, and is
converted into the product
Release of the product restores the
enzyme to its original conformation
Change in conformation of the enzyme
produces ‘induced fit’

Allosteric enzymes
Some enzymes possess a site, in addition to
the substrate site, known as the allosteric site
Binding of an allosteric molecule to allosteric
site changes the conformation of the enzyme
Enzymes having allosteric site are termed as
allosteric enzymes
EMB-RCG

EMB-RCG
Allosteric regulator
Allosteric modifier
Allosteric effector
The allosteric molecule
is also known as:

Some allosteric molecules:
Facilitate the conformational change
required for substrate binding
They are known as allosteric activators
(positive modifiers)
An example is N-acetylglutamate which
activates carbamoyl phosphate synthetase
EMB-RCG

Enzyme
Substrate site
Allosteric site
Substrate
Allosteric
activator
Allosteric activator
binds to enzyme;
substrate site
changes
Substrate can
now bind to
substrate site

Some allosteric regulators:
Prevent the conformational change required
for the binding of the substrate
Such regulators are known as allosteric
inhibitors (negative modifiers)
An example is glucose-6-phosphate which
inhibits hexokinase
EMB-RCG

Enzymes subject to allosteric inhibition are
usually present at the start of long pathways
The allosteric enzyme regulates the rate of
formation of the product
The allosteric inhibitor is generally the product
of the pathway

If the product is not being utilised, it
will accumulate
It inhibits the allosteric enzyme, and further
synthesis of the product ceases
When the product is used up, the allosteric
enzyme becomes free and active again
EMB-RCG

E1 is an allosteric enzyme,
and P is its allosteric inhibitor
EMB-RCG
S I1 I2 I3 I4 P
E1 E2 E3 E4 E5
Θ

Factors affecting the rates of
enzyme-catalysed reactions
Enzyme concentration
Substrate concentration
Coenzyme concentration
Temperature
pH
EMB-RCG

Enzyme concentration
EMB-RCG
An enzyme catalyses a reaction by
forming enzyme-substrate complex
Enzyme-substrate complex dissociates
into the enzyme and the product

E + S ↔ E S ↔ E + P
EMB-RCG
It is regenerated in its original form at
the end of the reaction
The enzyme may be considered to take
part in the reaction

Rate of the first reaction leading to formation
of ES is proportional to the product of molar
concentrations of E and S
Rate of formation of ES  [E] [S]
Rate of formation of E and P  [ES]
Rate of the second reaction leading to
formation of E and P is proportional to molar
concentration of ES

Therefore, the rate of the overall reaction
is proportional to the enzyme concentration
EMB-RCG
But this is true only if enough substrate
is available to combine with the enzyme

Rate of the reaction should be propor-
tional to substrate concentration also
But this is possible only if enough
enzyme is available to bind the substrate
However, the availability of enzymes in
the cells is limited
Substrate concentration
EMB-RCG

EMB-RCG
When the substrate concentration rises,
initially the velocity of the reaction rises
proportionately
But later the rise in velocity becomes
slower until a maximum velocity (Vmax) is
reached

Plot between substrate concentration and velocity
EMB-RCG
Vmax
Vmax
2
v
[S]Km

EMB-RCG
At Vmax, all the enzyme molecules are saturated
with substrate, and velocity cannot increase
further if the substrate concentration is raised
The substrate concentration at which the velocity
is half of Vmax is known as the Michaelis constant
(Km) of the enzyme

[ ]
[ ]
maxV Sv
Km S
=
+
.
EMB-RCG
The relationship between the velocity of the
reaction and the substrate concentration can
be expressed by Michaelis-Menten
equation

Hence, the equation may be rewritten as:
Vmax. [S]
v =
Km
Since both Vmax and Km are constant,
v  [S]
EMB-RCG
When the substrate concentration is very
low, the sum of Km and [S] is nearly
equal to Km as [S] is negligible

When the substrate concentration is very
high, the sum of Km and [S] is nearly
equal to [S] as Km is relatively negligible
[S] and [S] are cancelled;
the equation may be rewritten as:
v = Vmax
EMB-RCG
Vmax.[S]
v =
[S]
Hence, the equation may be rewritten as:

When the substrate concentration is
exactly equal to Km, the sum of Km and
[S] may be taken as 2 [S]
EMB-RCG
Thus, when the substrate concentration
is equal to Km, the velocity is half of Vmax
The equation may be rewritten as:
=
Vmax. [S] Vmax
v =
2[S] 2

Determination of Km
Every enzyme has got a
characteristic Km
Determination of Km is important in:
Study of
enzyme
kinetics
Assay of
enzyme
activity
Evaluation of
enzyme
inhibitors
EMB-RCG

EMB-RCG
Plotting v versus [S] is a lengthy process
The velocity has to be measured at a
number of substrate concentrations
The substrate concentration has to be
raised until Vmax is reached

EMB-RCG
Lineweaver and Burk devised a simple
method for determination of Km
Velocity is measured at a small number
(5-6) of substrate concentrations
A graph is plotted between the reciprocal
of v and the reciprocal of [S]

The
1/v versus 1/[S]
plot is known as:
Lineweaver-
Burk plot
Double
reciprocal plot
EMB-RCG

Vmax.[S]
v =
Km + [S]
EMB-RCG
Michaelis-Menten equation

=
Km + [S]1
v Vmax.[S]
EMB-RCG
or
1 Km 1 1
= +
v Vmax [S] Vmax

Michaelis-Menten equation is
inverted
or =
Km1
v Vmax.[S]
[S]
Vmax.[S]
+

This is the equation for a straight line
y (y-axis) is 1/v
a (slope of the line) is Km/Vmax
x (x-axis) is 1/[S]
b (y-intercept) is 1/Vmax
EMB-RCG
Vmax
1 Km 1 1
v Vmax [S]
=  +
y = a x + b

EMB-RCG
At the x-intercept (where the line meets
the x-axis), the value of y = 0
Therefore, at the x-intercept:
ax + b = 0
or ax = – b
or x = –
a
b

or
On substituting the values of b and a:
x =
1 Km
Vmax Vmax
- 
or x =
1
Vmax
-
Km
Vmax

x =
1
Km
-

Thus, the x-intercept i.e. the value of 1/[S] at
the x-intercept gives the value of 1/Km, and
the reciprocal of this will be the Km
11
1
1
Vmax
[S]Km
v
EMB-RCG

EMB-RCG
Allosteric enzymes do not follow
Michaelis-Menten equation
The v versus [S] plot of allosteric
enzymes is sigmoidal
This shows co-operative binding of
substrate to the enzyme

[S] → [S] →
↑
v
↑
v
Substrate concentration vs velocity plot
Normal
enzyme
Allosteric
enzyme

↑
v
[S] →
Positive effectors shift the plot to the left,
and negative effectors shift it to the right
EMB-RCG
Effect of allosteric activator and inhibitor on velocity

EMB-RCG
Kinetics of allosteric enzymes follow the
Hill equation
Hill plot is plotted between log v/Vmax–v
and log [S]
S50 of allosteric enzymes can be
determined from the Hill plot
S50 is the substrate concentration at
which the velocity is half of Vmax

EMB-RCG
In coenzyme-requiring reaction, coenzyme
concentration of also affects the velocity
Some coenzymes form an integral part of
the holoenzyme molecule
Other coenzymes act as co-substrates in
the reaction
Coenzyme concentration

EMB-RCG
If the coenzyme is an integral part of the
enzyme, the effect of coenzyme
concentration is same as that of enzyme
concentration
If the coenzyme acts as a second substrate,
the effect of coenzyme concentration is
similar to that of substrate concentration

EMB-RCG
To see the effect of temperature, velocity
of a reaction is measured at different
temperatures
A curve is plotted between velocity and
temperature
A bell-shaped curve is obtained
Temperature

↑
v
Temp →
Optimum
temp
│
Effect of temperature on velocity

EMB-RCG
When the temperature rises, the velocity
initially increases
This is due to increase in the kinetic
energy of the reactants

EMB-RCG
A further rise in temperature leads to
progressive denaturation of the enzyme
The velocity begins to decrease as the
enzyme gets denatured
The reaction practically stops when the
enzyme is completely denatured

EMB-RCG
The temperature at which the velocity is
maximum is known as the optimum
temperature of the enzyme
For all human enzymes, the optimum
temperature is 37°C

EMB-RCG
Temperature coefficient (Q10) of an
enzyme is the number of times the velocity
rises when temperature rises by 10°C
For most of the enzymes, the temperature
coefficient is two
This means that the velocity is doubled
when the temperatures rises by 10°C

EMB-RCG
If velocity is measured at different pH levels,
and is plotted against pH, a bell-shaped
curve is obtained
A change in pH alters electrical charges on
the enzyme molecules, and often on
substrate molecules as well
This may affect binding of the substrate to
the enzyme or the catalytic activity of the
enzyme or both
pH

↑
v
pH →
Optimum
pH
│
Effect of pH on velocity

EMB-RCG
At an optimum pH, the velocity of the
reaction is the highest because:
The electrical charges on the enzyme and
the substrate are the most suitable for:
Enzyme-substrate
binding
Catalysis

EMB-RCG
As we move away from the optimum pH,
the velocity of the reaction decreases
At extremely low or high pH, the enzyme
may be denatured
The optimum pH is different for different
enzymes

Enzyme inhibition
EMB-RCG
Catalytic activity of some enzymes can
be inhibited by certain compounds
Enzyme inhibition may be of two
types:
Competitive Non-competitive

Competitive inhibition
EMB-RCG
This is also known as substrate-analogue
inhibition
The inhibitor has a close structural
resemblance with the substrate
Inhibitor (I) binds to the substrate site of
enzyme forming enzyme-inhibitor (EI) complex

Substrate
Inhibitor
Products ‒‒

EMB-RCG
However, the inhibitor cannot form the
product
Thus, in the presence of the inhibitor, the
catalytic activity of the enzyme is inhibited
The inhibitor competes with the substrate
to bind to the enzyme

Substrate
+
Inhibitor
+
Enzyme
Inhibitor
+
Enzyme
Substrate
+
Enzyme
I IS
EE E

EMB-RCG
Due to competition between substrate and
inhibition, this type of inhibition is known as
competitive inhibition
Both ES and EI complexes are formed but
only ES can form the product
E + S + I ES + EI
E + P

EMB-RCG
The relative amounts of ES and EI complexes
depend upon the relative concentrations of the
substrate and the inhibitor
If the inhibitor concentration is higher, more EI
complex will be formed resulting in decreased
formation of the product
If the substrate concentration is higher, more ES
complex will be formed, and the inhibition will be
less

EMB-RCG
If a Lineweaver-Burk plot is plotted in the
presence of competitive inhibitor, the y-intercept
(1/Vmax) remains unchanged
However, the apparent Michaelis constant (K’m) is
higher (1/K’m is lower) in the presence of
competitive inhibitor

1/[S] →1
Km
1
Km´
In the absence
of inhibitor
1
Vmax
1
v
‒ In the presence
of inhibitor
↑
Competitive inhibition
‒

Competitive inhibitors do not affect the Vmax
But more substrate is required to reach the
Vmax in the presence of the inhibitor
The Vmax can be attained even in the
presence of the inhibitor

EMB-RCG
Efficacy of a competitive inhibitor can be
evaluated by measuring Km in the presence
and in the absence of the inhibitor
The inhibitors that raise the Km to a higher
degree are more effective inhibitors
Many competitive inhibitors are used as
drugs

EMB-RCG
Some competitive inhibitors
used as drugs are:
Amethopterin and aminopterin
Allopurinol
Physostigmine and neostigmine
Mevastatin and lovastatin

Amethopterin and aminopterin
Structural analogues of folic acid
Inhibitors of dihydrofolate reductase

H N2 N
N
|
OH
1
2
3
4
N
5
6
7
8
N
9 10
CH — N —2 — C — N — CH
| |
H COOH
COOH
|
CH2
|
CH2
|
O
||
H
|
Pteridine para-Amino-
benzoic acid
Glutamic
acid
Pteroylgutamic acid (folic acid)
CH3
Folic acid
Amethopterin
H N2 N
N
|
OH
1
2
3
4
N
5
6
7
8
N
9 10
CH —N —2 — C — N — CH
| |
COOH
COOH
|
CH2
|
CH2
|
O
||
H
|
CH3

Dihydrofolate
Tetrahydrofolate
Dihydrofolate
reductase
Folate
Dihydrofolate
reductase
EMB-RCG
Tetrahydrofolate is required for the synthesis
of purine and thymine nucleotides
NADPH + H+
NADPH+
NADPH + H+
NADPH+

Inhibition of dihydrofolate reductase decreases
the availability of nucleotides
If nucleotides are not available, DNA synthesis
and cell division are inhibited
Therefore, amethopterin and aminopterin are
used in cancer to suppress cell division
EMB-RCG

EMB-RCG
Allopurinol
Structural analogue of
hypoxanthine
Inhibitor of xanthine
oxidase

EMB-RCG
N
HN
O
||
C
C
CHC
N
H
H
C
N
N
HN
O
||
C
C
CHC
N
H
N
CH
Hypoxanthine Allopurinol

Hypoxanthine
Xanthine
oxidase
Uric acidXanthine
Xanthine
oxidase
Allopurinol is used to inhibit formation of
uric acid in gout, which results from over-
production of uric acid
Xanthine oxidase converts hypoxanthine
into xanthine, and xanthine into uric acid

EMB-RCG
Physostigmine and neostigmine
Structural analogues of
acetylcholine
Inhibitors of acetyl
cholinesterase

EMB-RCG
Acetylcholine + H2O
Acetate + Choline
Acetyl
cholinesterase

Physostigmine and neostigmine decrease
the breakdown of acetylcholine
They are used in the treatment of
myasthenia gravis, an auto-immune
disorder
Acetylcholine receptors are decreased in
number in myasthenia gravis
EMB-RCG

EMB-RCG
Mevastatin and Lovastatin
Structural analogues of HMG CoA
Inhibitors of HMG CoA reductase

HMG CoA Mevalonate
HMG CoA
reductase
Cholesterol
Therefore, mevastatin and lovastatin are used as
hypo-cholesterolaemic drugs
Inhibition of this reaction decreases the
synthesis of cholesterol
This is the key reaction in synthesis of cholesterol

Non-competitive inhibition
EMB-RCG
The non-competitive inhibitors have no
structural resemblance with the substrate
They do not compete with the substrate for
the substrate site on the enzyme
They bind to some other region of the
enzyme and render it inactive

Enzyme + Substrate +
Inhibitor
Enzyme + Substrate

EMB-RCG
Non-competitive inhibition may be reversible
or irreversible
Generally it is irreversible
Examples are iodoacetamide, p-chloro-
mercuribenzoate, heavy metals etc

EMB-RCG
In the presence of a non-competitive
inhibitor, Lineweaver-Burk plot shows that:
This means that non-competitive inhibitors
lower the Vmax but do not affect the Km
y-intercept is higher
x-intercept is unchanged

In the presence
of inhibitor
In the absence
of inhibitor
↑
1
v
1/[S] →1
Km
1
Vmax
1
V’max

Enzymes of diagnostic importance
EMB-RCG
A large number of enzymes are synthesized in
the cells
They are continuously released into circulation
due to normal wear and tear of cells
They are removed from circulation by
degradation or excretion

EMB-RCG
Non-functional plasma enzymes or
non-plasma-specific enzymes
Functional plasma enzymes or
plasma-specific enzymes
The circulating enzymes may be divided
into two types:
These enzymes are normally present in
circulation in minute concentrations

Functional plasma enzymes or plasma-
specific enzymes
EMB-RCG
These enzymes are purposely secreted
into circulation to perform specific catalytic
functions
These include lipoprotein lipase, blood
coagulation factors, complement proteins
etc

Non-functional plasma enzymes or non-
plasma-specific enzymes
EMB-RCG
These enzymes do not perform their
catalytic functions .in plasma
These are the intracellular enzymes
which enter the circulation when the cells
in which they are synthesized disintegrate

EMB-RCG
When breakdown of cells is occurring at normal
rate, non-functional enzymes are present in
plasma in very low concentrations
If the rate of destruction of cells increases due to
some pathological condition, these enzymes will
be released into circulation in large amounts
Their concentrations in plasma will rise many
times above normal

A non-functional plasma enzyme can pin-
point the site of the disease
EMB-RCG
IF
It has a selective tissue distribution
It is present in far higher concentration in
some tissues than elsewhere in the body
OR

EMB-RCG
Thus, it is the non-functional plasma
enzymes having a selective tissue
distribution which can give information
of diagnostic importance

Plasma enzymes that are established
diagnostic tools:
• Lactate dehydrogenase (LDH)
• Transaminases (GOT and GPT)
• Creatine kinase (CK)
• Gamma-glutamyl transpeptidase (GGT)
• Alkaline phosphatase (ALP)
• Acid phosphatase (ACP)
• Amylase
• Lipase
• Ceruloplasmin

EMB-RCG
Lactate
dehydrogenase
(LDH)
Catalyses
interconversion of
pyruvate and lactate
Tissue distribution
very wide
Concentration much
higher in
myocardium,
muscles and liver

EMB-RCG
Plasma LDH rises in:
Myocardial infarction
Viral hepatitis
Muscle injuries

EMB-RCG
In myocardial infarction:
Rise begins 24 hours after
infarction
Peak value is reached in
about three days
Level returns to normal in
about a week

EMB-RCG
Transaminases
Most important are glutamate oxaloacetate
transaminase (GOT) and glutamate pyruvate
transaminase (GPT)
Also known as aspartate aminotransferase
(AST) and alanine aminotransferase (ALT)
respectively
Present in high concentrations in myocardium,
liver and muscles

EMB-RCG
Serum GOT and GPT
are raised in:
Viral hepatitis
Muscle injuries

EMB-RCG
Rise in plasma GOT is more in
myocardial infarction and that in
GPT is more in viral hepatitis
Therefore
Concentration of GOT is higher than
that of GPT in myocardium while
the situation is reverse in liver

Creatine + ATP ↔ Creatine ~ ℗ + ADP
EMB-RCG
Creatine kinase (CK)
Also known as creatine
phosphokinase (CPK)
Catalyses interconversion of
creatine and creatine phosphate

EMB-RCG
Creatine kinase is
present in:
Myocardium
Muscles
Brain

EMB-RCG
Serum CK is raised in:
Myopathies
Muscle injuries

Rise begins within 3-6 hours after infarction
Peak is reached in 24 hours
Returns to normal in three days
More specific and early indicator than others
Serum CK in myocardial infarction

Days
Enzyme
level
Upper limit
of normal
0 1 2 3 4 5 6 7
CK GOT LDH

Begins to
rise in
Reaches
peak in
Returns to
normal in
Specificity
Myoglobin 1-3 hrs 4-6 hrs 18-24 hrs Low
Cardiac
Cardiac
troponin T
troponin I
4-6 hrs 18-36 hrs 5-15 days High
4-6 hrs 12-24 hrs 5-10 days High
Non-enzyme markers of myocardial
infarction

EMB-RCG
Is an early indicator of
alcoholic hepatitis
Serum level increases in most of
the liver diseases
Gamma-glutamyl
transpeptidase (GGT)
Transfers the g-glutamyl residue of
glutathione to other substrates

EMB-RCG
Alkaline phosphatase (ALP)
A group of enzymes that hydrolyse organic
phosphate esters at an alkaline pH
Released in circulation mainly from bones
and liver
Smaller amounts come from intestines and
placenta
Liver excretes ALP in bile

Viral hepatitis
Rickets
Hyperparathyroidism
Osteosarcoma
Bony metastases
EMB-RCG
Maximum rise in plasma ALP occurs
in obstructive jaundice
Smaller elevations occur in:

EMB-RCG
Acid phosphatase (ACP)
A group of enzymes that hydrolyse
organic phosphate esters at an acidic pH
The main source of ACP is the
prostate gland
Serum ACP is elevated in metastatic
carcinoma of prostate

EMB-RCG
Amylase
A digestive enzyme synthesised in
the pancreas and the parotid gland
Sharp elevation of serum amylase
occurs in acute pancreatitis
A smaller elevation occurs in
acute parotitis

EMB-RCG
Lipase
A lipolytic enzyme released into
circulation from the pancreas
Serum lipase rises in acute
pancreatitis

EMB-RCG
Ceruloplasmin
A copper-containing protein having
ferroxidase activity
Absent or almost absent in serum in
Wilson’s disease (hepatolenticular
degeneration)

Isoenzymes
EMB-RCG
Enzymes that:
Exist in multiple molecular forms
Catalyse the same reaction
Differ slightly in physical, chemical
and immunological properties

EMB-RCG
Isoenzymes possess quaternary
structure
They are made up of two or more
different subunits
The subunits have slightly different
primary structures

EMB-RCG
Isoenzymes Usually differ in their Km and
Vmax values
They may differ in how they are
regulated
They help in fine-tuning of metabolism

EMB-RCG
Isoenzymes can be separated by:
Electrophoresis
Chromatography
Immunochemical methods

EMB-RCG
The tissue distribution of isoenzymes
is highly specific
Measurement of isoenzymes can be
of great diagnostic importance

EMB-RCG
Isoenzymes of diagnostic
importance include:
Creatine kinase
Alkaline phosphatase

H subunit M subunit
EMB-RCG
First enzyme shown to exist in the form of
five isoenzymes by Markert (1957)
The enzyme is a tetramer made up of
two types of subunits – H and M

EMB-RCG
• HHHH
• HHHM
• HHMM
• HMMM
• MMMM
The subunits can form five different
tetramers (isoenzymes):
or LD5 or LDH5
or LD4 or LDH4
or LD3 or LDH3
or LD2 or LDH2
or LD1 or LDH1

EMB-RCG
The LD isoenzymes in plasma can be
separated by electrophoresis
The normal pattern of LD isoenzymes in
serum is LD2 >LD1 >LD3 >LD4 >LD5

EMB-RCG
The predominant isoenzymes in myocardium
are LD1 and LD2
Both are raised in myocardial infarction
The rise in LD1 is greater than that in LD2
Therefore, the pattern of plasma LD iso-
enzymes becomes LD1 >LD2 >LD3 >LD4 >LD5

EMB-RCG
LD5 is the predominant isoenzyme in liver
Therefore, LD5 is raised in viral
hepatitis

Creatine kinase
B subunit M subunit
EMB-RCG
A dimer made up of two types of
subunits
The subunits are – B and M

EMB-RCG
Three different dimers (isoenzymes) can
be formed from these two subunits:
• BB or CK1 or CK-BB
• MB or CK2 or CK-MB
• MM or CK3 or CK-MM

EMB-RCG
CK-MB is commonly measured by immuno-
inhibition
Serum is treated with anti-M subunit antibody
CK-MM is inhibited
The residual enzyme is taken to be CK-MB
as CK-BB is negligible

The major isoenzyme in myocardium is CK-MB
In plasma, CK-MB is less than 3% of total CK
CK-MB is raised in myocardial infarction
CK-BB
CK-MB
CK-MM

EMB-RCG
CK-BB, CK-MB and CK-MM are present in
cytosol
A different CK is present in mitochondria –
mitochondrial CK (CK-MT or CK-Mi)

EMB-RCG
CK-MT has two isoforms: CK-MT1 and
CK-MT2
CK-MT1 is ubiquitous
CK-MT2 is present in skeletal and heart
muscle

EMB-RCG
CK-MT can exist as a dimer or an octamer
The dimeric and octameric forms are
inter-changeable

EMB-RCG
CK-MT1 and CK-MT2 are encoded by
different genes
Thus, there are four genes for CK
subunits
These are CK-M, CK-B, CK-MT1 and CK-
MT2

EMB-RCG
CK-M and CK-B genes encode the
cytosolic enzyme
CK-MT1 and CK-MT2 genes encode the
mitochondrial enzyme
CK-MT1 and CK-MT2 isoenzymes have no
diagnostic importance

EMB-RCG
Bone, liver, intestine and placenta form
different isoenzymes
ALP isoenzymes are commonly separated
by electrophoresis
The liver isoenzyme moves the fastest
It occupies the same position as a2-globulin
Alkaline phosphatase

EMB-RCG
The bone ALP closely follows the liver
ALP
The placental isoenzyme follows the bone
isoenzyme
The intestinal isoenzyme is the slowest
moving

EMB-RCG
The liver ALP is raised in liver cancer and
biliary obstruction
The bone ALP is raised in osteoblastic
bone tumours and Paget’s disease
The placental and intestinal isoenzymes
have no diagnostic importance

EMB-RCG
Two atypical ALP isoenzymes are seen in
some cancers
These are Regan isoenzyme and Nagao
isoenzyme
These two resemble the placental
isoenzyme

EMB-RCG
Regan isoenzyme is raised in cancer of
breast, lungs, colon, uterus and ovaries
Nagao isoenzyme is raised in germ cell
cancer of the testes

EMB-RCG
Metabolic pathways need precise regulation
Regulation ensures adequacy of products with
no wastage of raw materials
Requirements of the organism keep on changing
Regulatory mechanisms must be responsive
to these changes
Regulation of enzymes

Concentrations of enzymes
Catalytic activity of enzymes
Metabolic pathways are regulated by
changing one of the following:
Enzymes play a crucial role in the
regulatory mechanisms

The regulation involves one or a few “key”
enzymes in a pathway
EMB-RCG
The rate-limiting step in the pathway
The committed step in the pathway
The key enzyme (or regulatory enzyme) may
catalyse:

EMB-RCG
Rate-limiting
step
An early reaction
that controls the
availability of
substrates for the
subsequent
reactions
Committed
step
The earliest
irreversible
reaction unique
to the pathway

Regulation of enzyme concentration
EMB-RCG
Some pathways are regulated by changing the
concentrations of the key enzymes
The rates of reactions would change accordingly
Concentration of an enzyme may be changed by
altering its synthesis or its degradation
Regulation of enzyme synthesis is commoner

Regulation of enzyme synthesis
EMB-RCG
Enzyme synthesis may be
regulated by:
Induction of enzyme synthesis
Repression of enzyme synthesis
Conversion of proenzyme into
enzyme

EMB-RCG
Enzymes may be divided into:
Constitutive
enzymes
Inducible
enzymes
Induction

EMB-RCG
Constitutive
enzymes
Inducible
enzymes
Continuously
synthesized
Synthesized only
when required
Always present in the
cell
Synthesized when
inducer enters the cell

EMB-RCG
Inducer may be the substrate for the
enzyme or may be a gratuitous inducer
A gratuitous inducer is one which is not a
substrate for the enzyme

EMB-RCG
The inducer acts on DNA, and increases
the expression of the gene that encodes
the enzyme
An example is induction of key enzymes
of gluconeogenesis by glucocorticoid
hormones

EMB-RCG
Synthesis of some enzymes is regulated by
repression
Transcription of gene encoding the enzyme
is blocked by a repressor
The repressor is made up of apo-repressor
and co-repressor
Repression

EMB-RCG
Apo-repressor is a protein always
present in the cell
When co-repressor enters or
accumulates in the cell, it combines with
apo-repressor to form the repressor
The co-repressor is generally the
product of the pathway

EMB-RCG
An example is regulation of haem synthesis
by d-aminolevulinic acid synthetase
Haem acts as co-repressor, and represses the
synthesis of this early enzyme in the pathway
When the product is used up, the repression is
relieved (derepression)

Conversion of proenzyme into enzyme
EMB-RCG
Sometimes, the concentration of enzymes needs
to be increased quickly
For example, when food enters stomach,
concentration of pepsin needs to be raised quickly
This can not be done by induction or derepression
which are slow processes

EMB-RCG
The enzyme is synthesized in the form of an
precursor, pepsinogen
Pepsinogen is an inactive proenzyme
The proenzyme will not digest the mucosal
proteins

EMB-RCG
Entry of food in the stomach generates some
signals
These signals convert pepsinogen into pepsin
The enzyme concentration is raised quickly

Proenzyme
Enzyme
Peptide
Proteolysis
Active site
(masked) →
Active site
(exposed) →
Proteolytic activation of proenzyme
Substrate

EMB-RCG
Enzyme concentration may also be
regulated by altering its breakdown
Increased breakdown will decrease the
concentration of the enzyme
Decreased breakdown will increase the
concentration of the enzyme
Regulation of enzyme degradation

EMB-RCG
Regulation of degradation is not common in
higher organisms
A few examples are seen in starvation in which
nutrients need to be conserved
Concentration of some enzymes is increased by
decreasing their breakdown
An example of such enzyme is tryptophan
pyrrolase

EMB-RCG
Regulation of catalytic activity of enzymes
Enzyme concentration remains unchanged
but its catalytic activity is altered
The catalytic activity may be altered by:
Allosteric regulation
of the enzyme
Covalent modification
of the enzyme

EMB-RCG
This mechanism is used in some long
metabolic pathways
The substrate is converted into a product by
a series of reactions
The earliest functionally irreversible reaction is
catalysed by an allosteric enzyme

S I1 I2 I3 I4 P
E1 E2 E3 E4 E5
EMB-RCG
Usually, the product of the pathway is
the allosteric inhibitor of the enzyme
When the product accumulates, it
inhibits the allosteric enzyme
Θ

EMB-RCG
When the product is used up, the inhibition is
relieved
In this way, the rate of synthesis of product is
regulated according to the rate of its utilisation
If the pathway has a number of irreversible steps,
regulation may occur at a number of steps

EMB-RCG
Some enzymes are regulated by positive
allosteric modulation (activation)
An example is regulation of carbamoyl phosphate
synthetase I (mitochondrial)
This enzyme is allosterically activated by
N-acetylglutamate

EMB-RCG
Many enzymes are regulated by negative
allosteric modulation (inhibition)
An example is asparate transcarbamoylase
It is an early enzyme in de novo synthesis of
pyrimidine nucleotides
It is inhibited by cytidine triphosphate, a product
of the pathway

EMB-RCG
A few enzymes are subject to positive as well as
negative allosteric regulation
Phosphofructokinase-1, a regulatory enzyme in
the glycolytic pathway, is subject to:
Allosteric activation
by AMP
Allosteric inhibition
by ATP

EMB-RCG
The enzymes regulated by this mechanism can
exist in two forms
These can be converted into each other by a
covalent modification of the enzyme molecule
The most common covalent modification is
addition or removal of phosphate

Phosphate is usually added to or removed from a
serine residue in the enzyme
A protein kinase adds phosphate, and a protein
phosphatase removes phosphate
P
Protein kinase
Protein phosphatase
H2O
ATP ADP
Pi
ENZYME‒Ser‒OH ENZYME‒Ser‒O‒
(Dephosphorylated
enzyme)
(Phosphorylated
enzyme)

EMB-RCG
One form, either phosphorylated or dephospho-
rylated, is active and the other is inactive
Whether the enzyme is active or inactive
depends upon the relative activities of protein
kinase and protein phosphatase
These, in turn, are controlled by hormones acting
through second messengers

EMB-RCG
An example is glycogen synthetase ‒ active in
the dephosphorylated form and inactive in the
phosphorylated form
Another example is glycogen phosphorylase ‒
inactive in the dephosphorylated form and active
in the phosphorylated form

For example, acetyl CoA carboxylase is
subject to:
Repression
Induction
Some enzymes are regulated by
multiple mechanisms

Assay of enzymes
EMB-RCG
Measurement of enzyme levels is often required
for diagnostic/academic purposes
Enzyme concentrations are very minute
Isolation and purification of individual enzymes is
laborious
Therefore, direct measurement of enzyme
concentrations is very difficult

EMB-RCG
Enzyme concentrations are measured
indirectly
Velocity of the enzyme-catalysed reaction is
measured
Conditions are such that rate of reaction is
proportional to the enzyme concentration

EMB-RCG
To keep temperature constant, reaction is carried
out in a fixed-temperature water-bath or incubator
Optimum pH is maintained by using a buffer
Substrate concentration is kept constant and high
Under such conditions, rate of the reaction will be
proportional to the enzyme concentration

EMB-RCG
The rate of the reaction can be
determined by measuring:
The rate of disappearance
of the substrate
Rate of appearance of the
product

EMB-RCG
In endpoint methods:
The reaction is carried out for a fixed
period
Initial and final concentrations of the
substrate or the product are measured

EMB-RCG
In kinetic methods, the concentration of the
substrate or the product is measured at
regular intervals for a brief period
The result in either case is expressed in
arbitrary units of enzyme activity rather
than enzyme concentration

EMB-RCG
Many enzymes are used as tools in
diagnostic and research laboratories
Glucose oxidase and peroxidase are
used for measuring glucose concentration
Hexokinase and glucose-6-phosphate
dehydrogenase are also used for
measuring glucose concentration
Enzymes as laboratory tools

EMB-RCG
Cholesterol esterase, cholesterol oxidase
and peroxidase are used for measuring
cholesterol concentration
Lipase, glycerol kinase, glycerol phosphate
oxidase and peroxidase are used for
measuring triglyceride concentration

EMB-RCG
Urease is used for measurement of urea
concentration
Uricase is used for measuring uric acid
concentration
Enzymes like peroxidase and alkaline
phosphatase are used to label antibodies
in ELISA

EMB-RCG
A number of enzymes are used in
recombinant DNA technology e.g.
Restriction endonuclease
DNA ligase
Terminal transferase
S1 nuclease
Reverse transcriptase
Taq polymerase

Enzymes as drugs
EMB-RCG
Some human, animal, plant and microbial
enzymes are used as drugs also
Digestive enzymes e.g. diastase, papain, pepsin,
chymotrypsin etc are used to aid digestion
Pancreatic amylase, lipase and proteases are
used in the treatment of pancreatic insufficiency

Serratiopeptidase is a bacterial proteolytic
enzyme
It is used to remove dead tissue from the
site of inflammation to accelerate healing
It is also used to reduce inflammation,
oedema and pain

Hyaluronidase catalyses hydrolysis of
hyaluronic acid
Hyaluronidase injections are used to
facilitate delivery of other injectable drugs

Asparaginase is used in the chemotherapy
of leukaemia
Leukaemic cells are deficient in asparagine
synthetase
They are dependent on pre-formed
asparagine

Asparaginase converts asparagine into
aspartate
This deprives the leukaemic cells of an
essential nutrient

EMB-RCG
Thrombolytic drugs used to clear
blockage of blood vessels are:
Streptokinase
Urokinase
Tissue plasminogen activator

Enzymes

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Enzymes

Similar to Enzymes (20)

More from Ramesh Gupta

More from Ramesh Gupta (20)

Recently uploaded

Recently uploaded (20)

Enzymes